Abstract:

Methods of controlling a backlight unit including a plurality of solid
state light emitting devices include receiving a request to set a color
point of the backlight unit at a requested color point, and determining
if the requested color point is within an acceptable range. In response
to the requested color point being outside the acceptable range, a
modified color point is selected in response to the requested color
point, and a color point of the backlight unit is set at the modified
color point. Corresponding solid state lighting units are also disclosed.

Claims:

1. A method of controlling a lighting panel including a plurality of solid
state light emitting devices, comprising:receiving a request to set a
color point of the lighting panel at a requested color point;determining
if the requested color point is within an acceptable range;in response to
the requested color point being outside the acceptable range, selecting a
modified color point in response to the requested color point; andsetting
a color point of the lighting panel at the modified color point.

2. The method of claim 1, wherein the acceptable range is defined with
reference to a two-dimensional color space.

3. The method of claim 2, wherein the acceptable range is defined as a
rectangle within the two-dimensional color space.

4. The method of claim 3, wherein the color space is represented by a 1931
CIE chromaticity diagram, and wherein the acceptable range is defined as
a chromaticity point having coordinates (x,y), where
xlim1.ltoreq.x≦xlim2 and ylim1.ltoreq.y≦ylim2.

5. The method of claim 4, wherein 0.26.ltoreq.x≦0.38 and
0.26.ltoreq.y≦0.38.

6. The method of claim 4, further comprising:determining if an
x-coordinate of the requested color point falls within an acceptable
range of x-coordinates; andif the x-coordinate of the requested color
point does not fall within the acceptable range of x-coordinates, setting
the x-coordinate of the modified color point as the closest x-coordinate
in the range of acceptable x-coordinates to the x-coordinate of the
requested color point.

7. The method of claim 6, further comprising:determining if a y-coordinate
of the requested color point falls within an acceptable range of
y-coordinates; andif the y-coordinate of the requested color point does
not fall within the acceptable range of x-coordinates, setting the
y-coordinate of the modified color point as the closest y-coordinate in
the range of acceptable y-coordinates to the y-coordinate of the
requested color point.

8. The method of claim 2, wherein the acceptable range includes color
points within a distance r from a reference color point.

9. The method of claim 8, wherein selecting the modified color point
comprises translating the requested color point along a line between the
modified color point and the reference color point until the translated
color point falls within the acceptable range.

10. The method of claim 2, wherein the acceptable range is defined as
including color points falling within a region described by a regular or
irregular polygon.

11. The method of claim 10, wherein selecting the modified color point
comprises translating the requested color point toward a closest point on
a surface of the polygon until the translated color point falls within
the acceptable range.

12. The method of claim 10, wherein selecting the modified color point
comprises translating the requested color point toward a reference color
point until the translated color point falls within the acceptable range.

13. The method of claim 2, wherein the acceptable range is defined as
color points that are within a predetermined distance from a blackbody
radiation curve.

14. The method of claim 13, wherein selecting the modified color point
comprises translating the requested color point toward a closest point on
the blackbody radiation curve until the translated color point falls
within the acceptable range.

15. The method of claim 13, wherein selecting the modified color point
comprises translating the requested color point toward a reference color
point until the translated color point falls within the acceptable range.

16. A solid state lighting device, comprising:a lighting panel comprising
a plurality of solid state light emitting devices; anda controller
configured to control light output of the solid state light emitting
devices, to receive a requested color point for the lighting panel, to
determine if the requested color point is within an acceptable range, to
select a modified color point in response to the requested color point
being outside the acceptable range, and to set a color point of the
lighting device at the modified color point.

17. The solid state lighting device of claim 16, further comprising:a
photosensor configured to measure a light output of the lighting panel
and to provide the light output measurement to the controller in a closed
loop control system.

18. The solid state lighting device of claim 16, wherein the acceptable
range is defined to include a circle and/or a polygon within a
two-dimensional color space.

19. The solid state lighting device of claim 18, wherein the controller is
configured to select the modified color point by translating the
requested color point toward a closest point of the polygon and/or circle
until the translated color point falls within the acceptable range.

20. The solid state lighting device of claim 17, wherein the controller is
configured to select the modified color point by translating the
requested color point toward a reference color point until the translated
color point falls within the acceptable range.

21. A method of controlling a lighting panel including a plurality of
solid state light emitting devices, comprising:receiving a request to set
a color point of the backlight unit at a requested color
point;determining if the requested color point is within an acceptable
range;in response to the requested color point being outside the
acceptable range, selecting a modified color point in response to the
requested color point; andsetting a color point of the backlight unit at
the modified color point;wherein the acceptable range is defined by a
rectangle within a two-dimensional color space.

22. The method of claim 1, wherein the acceptable range of color points is
smaller than an actual color gamut of the backlight unit, and wherein
selecting a modified color point comprises selecting a modified color
point that is within the acceptable range of color points.

23. The solid state backlight unit of claim 16, wherein the controller is
configured to determine if the requested color point is within an
acceptable range of color points that is smaller than an actual color
gamut of the backlight unit, and to select a modified color point that is
within the acceptable range in response to the requested color point
being outside the acceptable range.

24. The method of claim 21, wherein the acceptable range of color points
is smaller than an actual color gamut of the backlight unit, and wherein
selecting a modified color point comprises selecting a modified color
point that is within the acceptable range of color points.

Description:

RELATED APPLICATIONS

[0001]This application claims the benefit of U.S. patent application Ser.
No. 11/751,263 filed on May 21, 2007, in the U.S. Patent and Trademark
Office, the disclosure of which is incorporated herein in its entirety by
reference as if set forth fully herein.

FIELD OF THE INVENTION

[0002]The present invention relates to solid state lighting, and more
particularly to adjustable solid state lighting panels and to systems and
methods for adjusting the light output of solid state lighting panels.

BACKGROUND

[0003]Solid state lighting arrays are used for a number of lighting
applications. For example, solid state lighting panels including arrays
of solid state lighting devices have been used as direct illumination
sources, such as in architectural and/or accent lighting. A solid state
lighting device may include, for example, a packaged light emitting
device including one or more light emitting diodes (LEDs). Inorganic LEDs
typically include semiconductor layers forming p-n junctions. Organic
LEDs (OLEDs), which include organic light emission layers, are another
type of solid state light emitting device. Typically, a solid state light
emitting device generates light through the recombination of electronic
carriers, i.e. electrons and holes, in a light emitting layer or region.

[0004]Solid state lighting panels are commonly used as backlights for
small liquid crystal display (LCD) display screens, such as LCD display
screens used in portable electronic devices. In addition, there has been
increased interest in the use of solid state lighting panels as
backlights for larger displays, such as LCD television displays.

[0005]For smaller LCD screens, backlight assemblies typically employ white
LED lighting devices that include a blue-emitting LED coated with a
wavelength conversion phosphor that converts some of the blue light
emitted by the LED into yellow light. The resulting light, which is a
combination of blue light and yellow light, may appear white to an
observer. However, while light generated by such an arrangement may
appear white, objects illuminated by such light may not appear to have a
natural coloring, because of the limited spectrum of the light. For
example, because the light may have little energy in the red portion of
the visible spectrum, red colors in an object may not be illuminated well
by such light. As a result, the object may appear to have an unnatural
coloring when viewed under such a light source.

[0006]The color rendering index of a light source is an objective measure
of the ability of the light generated by the source to accurately
illuminate a broad range of colors. The color rendering index ranges from
essentially zero for monochromatic sources to nearly 100 for incandescent
sources. Light generated from a phosphor-based solid state light source
may have a relatively low color rendering index.

[0007]For large-scale backlight and illumination applications, it is often
desirable to provide a lighting source that generates a white light
having a high color rendering index, so that objects and/or display
screens illuminated by the lighting panel may appear more natural.
Accordingly, such lighting sources may typically include an array of
solid state lighting devices including red, green and blue light emitting
devices. When red, green and blue light emitting devices are energized
simultaneously, the resulting combined light may appear white, or nearly
white, depending on the relative intensities of the red, green and blue
sources. There are many different hues of light that may be considered
"white." For example, some "white" light, such as light generated by
sodium vapor lighting devices, may appear yellowish in color, while other
"white" light, such as light generated by some fluorescent lighting
devices, may appear more bluish in color.

[0008]The chromaticity of a particular light source may be referred to as
the "color point" of the source. For a white light source, the
chromaticity may be referred to as the "white point" of the source. The
white point of a white light source may fall along a locus of
chromaticity points corresponding to the color of light emitted by a
black-body radiator heated to a given temperature. Accordingly, a white
point may be identified by a correlated color temperature (CCT) of the
light source, which is the temperature at which the heated black-body
radiator matches the hue of the light source. White light typically has a
CCT of between about 4000K and 8000K. White light with a CCT of 4000K has
a yellowish color, while light with a CCT of 8000K is more bluish in
color.

[0009]For larger display and/or illumination applications, multiple solid
state lighting tiles may be connected together, for example, in a two
dimensional array, to form a larger lighting panel. Unfortunately,
however, the hue of white light generated may vary from tile to tile,
and/or even from lighting device to lighting device. Such variations may
result from a number of factors, including variations of intensity of
emission from different LEDs, and/or variations in placement of LEDs in a
lighting device and/or on a tile. Accordingly, in order to construct a
multi-tile display panel that produces a consistent hue of white light
from tile to tile, it may be desirable to measure the hue and saturation,
or chromaticity, of light generated by a large number of tiles, and to
select a subset of tiles having a relatively close chromaticity for use
in the multi-tile display. This may result in decreased yields and/or
increased inventory costs for a manufacturing process.

[0010]Moreover, even if a solid state display/lighting tile has a
consistent, desired hue of light when it is first manufactured, the hue
and/or brightness of solid state devices within the tile may vary
non-uniformly over time and/or as a result of temperature variations,
which may cause the overall color point of the panel to change over time
and/or may result in non-uniformity of color across the panel. In
addition, a user may wish to change the light output characteristics of a
display panel in order to provide a desired hue and/or brightness level.

SUMMARY

[0011]Some embodiments of the invention provide methods of controlling a
backlight unit including a plurality of solid state light emitting
devices. The methods include receiving a request to set a color point of
the backlight unit at a requested color point, and determining if the
requested color point is within an acceptable range. In response to the
requested color point being outside the acceptable range, a modified
color point is selected in response to the requested color point, and a
color point of the backlight unit is set at the modified color point.

[0012]The acceptable range may be defined with reference to a
two-dimensional color space. For example, the acceptable range may be
defined as a rectangle within the two-dimensional color space.

[0013]The color space may be represented by a 1931 CIE chromaticity
diagram, and the acceptable range may be defined as a chromaticity point
having coordinates (x,y), where xlim1≦x≦xlim2 and
ylim1≦y≦ylim2. In some embodiments, the color space may be
defined as 0.26≦x≦0.38 and 0.26≦y≦0.38.

[0014]The methods may further include determining if an x-coordinate of
the requested color point falls within an acceptable range of
x-coordinates. If the x-coordinate of the requested color point does not
fall within the acceptable range of x-coordinates, the x-coordinate of
the modified color point may be set as the closest x-coordinate in the
range of acceptable x-coordinates to the x-coordinate of the requested
color point.

[0015]The methods may further include determining if a y-coordinate of the
requested color point falls within an acceptable range of y-coordinates.
If the y-coordinate of the requested color point does not fall within the
acceptable range of x-coordinates, the y-coordinate of the modified color
point may be set as the closest y-coordinate in the range of acceptable
y-coordinates to the y-coordinate of the requested color point.

[0016]The acceptable range may include color points within a distance r
from a reference color point. Selecting the modified color point may
include translating the requested color point along a line between the
modified color point and the reference color point until the translated
color point falls within the acceptable range.

[0017]The acceptable range may be defined as including color points
falling within a region described by a regular or irregular polygon.
Selecting the modified color point may include translating the requested
color point toward a closest point on a surface of the polygon until the
translated color point falls within the acceptable range. In some
embodiments, selecting the modified color point may include translating
the requested color point toward a reference color point until the
translated color point falls within the acceptable range.

[0018]The acceptable range may be defined as color points that are within
a predetermined distance from a blackbody radiation curve. Selecting the
modified color point may include translating the requested color point
toward a closest point on the blackbody radiation curve until the
translated color point falls within the acceptable range. In some
embodiments, selecting the modified color point may include translating
the requested color point toward a reference color point until the
translated color point falls within the acceptable range.

[0019]A solid state backlight unit according to some embodiments of the
invention includes a lighting panel including a plurality of solid state
light emitting devices, and a controller configured to control light
output of the solid state light emitting devices. The controller is
further configured to receive a requested color point for the lighting
panel, to determine if the requested color point is within an acceptable
range, to select a modified color point in response to the requested
color point being outside the acceptable range, and to set a color point
of the backlight unit at the modified color point.

[0020]The solid state backlight unit may further include a photosensor
configured to measure a light output of the lighting panel and to provide
the light output measurement to the controller in a closed loop control
system.

[0021]The acceptable range may be defined to include a circle and/or a
polygon within a two-dimensional color space.

[0022]The controller may be configured to select the modified color point
by translating the requested color point toward a closest point of the
polygon and/or circle until the translated color point falls within the
acceptable range.

[0023]In some embodiments, the controller may be configured to select the
modified color point by translating the requested color point toward a
reference color point until the translated color point falls within the
acceptable range.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and constitute a
part of this application, illustrate certain embodiment(s) of the
invention. In the drawings:

[0025]FIG. 1 is a front view of a solid state lighting tile in accordance
with some embodiments of the invention;

[0026]FIG. 2 is a top view of a packaged solid state lighting device
including a plurality of LEDs in accordance with some embodiments of the
invention;

[0027]FIG. 3 is a schematic circuit diagram illustrating the electrical
interconnection of LEDs in a solid state lighting tile in accordance with
some embodiments of the invention;

[0028]FIG. 4A is a front view of a bar assembly including multiple solid
state lighting tiles in accordance with some embodiments of the
invention;

[0029]FIG. 4B is a front view of a lighting panel in accordance with some
embodiments of the invention including multiple bar assemblies;

[0030]FIG. 5 is a schematic block diagram illustrating a lighting panel
system in accordance with some embodiments of the invention;

[0031]FIGS. 6A-6D are a schematic diagrams illustrating possible
configurations of photosensors on a lighting panel in accordance with
some embodiments of the invention;

[0032]FIGS. 7 and 8 are schematic diagrams illustrating elements of a
lighting panel system according to some embodiments of the invention;

[0033]FIGS. 9A-9D are a graphs of a CIE color chart illustrating certain
aspects of the invention; and

[0034]FIG. 10 is a flowchart illustrating systems and/or methods according
to some embodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0035]Embodiments of the present invention now will be described more
fully hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may, however, be
embodied in many different forms and should not be construed as limited
to the embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and will
fully convey the scope of the invention to those skilled in the art. Like
numbers refer to like elements throughout.

[0036]It will be understood that, although the terms first, second, etc.
may be used herein to describe various elements, these elements should
not be limited by these terms. These terms are only used to distinguish
one element from another. For example, a first element could be termed a
second element, and, similarly, a second element could be termed a first
element, without departing from the scope of the present invention. As
used herein, the term "and/or" includes any and all combinations of one
or more of the associated listed items.

[0037]It will be understood that when an element such as a layer, region
or substrate is referred to as being "on" or extending "onto" another
element, it can be directly on or extend directly onto the other element
or intervening elements may also be present. In contrast, when an element
is referred to as being "directly on" or extending "directly onto"
another element, there are no intervening elements present. It will also
be understood that when an element is referred to as being "connected" or
"coupled" to another element, it can be directly connected or coupled to
the other element or intervening elements may be present. In contrast,
when an element is referred to as being "directly connected" or "directly
coupled" to another element, there are no intervening elements present.

[0038]Relative terms such as "below" or "above" or "upper" or "lower" or
"horizontal" or "vertical" may be used herein to describe a relationship
of one element, layer or region to another element, layer or region as
illustrated in the figures. It will be understood that these terms are
intended to encompass different orientations of the device in addition to
the orientation depicted in the figures.

[0039]The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the
invention. As used herein, the singular forms "a", "an" and "the" are
intended to include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" "comprising," "includes" and/or "including" when used herein,
specify the presence of stated features, integers, steps, operations,
elements, and/or components, but do not preclude the presence or addition
of one or more other features, integers, steps, operations, elements,
components, and/or groups thereof.

[0040]Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this invention
belongs. It will be further understood that terms used herein should be
interpreted as having a meaning that is consistent with their meaning in
the context of this specification and the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly so
defined herein.

[0041]The present invention is described below with reference to flowchart
illustrations and/or block diagrams of methods, systems and computer
program products according to embodiments of the invention. It will be
understood that some blocks of the flowchart illustrations and/or block
diagrams, and combinations of some blocks in the flowchart illustrations
and/or block diagrams, can be implemented by computer program
instructions. These computer program instructions may be stored or
implemented in a microcontroller, microprocessor, digital signal
processor (DSP), field programmable gate array (FPGA), a state machine,
programmable logic controller (PLC) or other processing circuit, general
purpose computer, special purpose computer, or other programmable data
processing apparatus such as to produce a machine, such that the
instructions, which execute via the processor of the computer or other
programmable data processing apparatus, create means for implementing the
functions/acts specified in the flowchart and/or block diagram block or
blocks.

[0042]These computer program instructions may also be stored in a computer
readable memory that can direct a computer or other programmable data
processing apparatus to function in a particular manner, such that the
instructions stored in the computer readable memory produce an article of
manufacture including instruction means which implement the function/act
specified in the flowchart and/or block diagram block or blocks.

[0043]The computer program instructions may also be loaded onto a computer
or other programmable data processing apparatus to cause a series of
operational steps to be performed on the computer or other programmable
apparatus to produce a computer implemented process such that the
instructions which execute on the computer or other programmable
apparatus provide steps for implementing the functions/acts specified in
the flowchart and/or block diagram block or blocks. It is to be
understood that the functions/acts noted in the blocks may occur out of
the order noted in the operational illustrations. For example, two blocks
shown in succession may in fact be executed substantially concurrently or
the blocks may sometimes be executed in the reverse order, depending upon
the functionality/acts involved. Although some of the diagrams include
arrows on communication paths to show a primary direction of
communication, it is to be understood that communication may occur in the
opposite direction to the depicted arrows.

[0044]Referring now to FIG. 1, a solid state lighting tile 10 may include
thereon a number of solid state lighting elements 12 arranged in a
regular and/or irregular two dimensional array. The tile 10 may include,
for example, a printed circuit board (PCB) on which one or more circuit
elements may be mounted. In particular, a tile 10 may include a metal
core PCB (MCPCB) including a metal core having thereon a polymer coating
on which patterned metal traces (not shown) may be formed. MCPCB
material, and material similar thereto, is commercially available from,
for example, The Bergquist Company. The PCB may further include heavy
clad (4 oz. copper or more) and/or conventional FR-4 PCB material with
thermal vias. MCPCB material may provide improved thermal performance
compared to conventional PCB material. However, MCPCB material may also
be heavier than conventional PCB material, which may not include a metal
core.

[0045]In the embodiments illustrated in FIG. 1, the lighting elements 12
are multi-chip clusters of four solid state emitting devices per cluster.
In the tile 10, four lighting elements 12 are serially arranged in a
first path 20, while four lighting elements 12 are serially arranged in a
second path 21. The lighting elements 12 of the first path 20 are
connected, for example via printed circuits, to a set of four anode
contacts 22 arranged at a first end of the tile 10, and a set of four
cathode contacts 24 arranged at a second end of the tile 10. The lighting
elements 12 of the second path 21 are connected to a set of four anode
contacts 26 arranged at the second end of the tile 10, and a set of four
cathode contacts 28 arranged at the first end of the tile 10.

[0046]The solid state lighting elements 12 may include, for example,
organic and/or inorganic light emitting devices. An exemplary solid state
lighting element 12' for high power illumination applications is
illustrated in FIG. 2. A solid state lighting element 12' may comprise a
packaged discrete electronic component including a carrier substrate 13
on which a plurality of LED chips 16A-16D are mounted. In other
embodiments, one or more solid state lighting elements 12 may comprise
LED chips 16A-16D mounted directly onto electrical traces on the surface
of the tile 10, forming a multi-chip module or chip on board assembly.
Suitable tiles are disclosed in commonly assigned U.S. patent application
Ser. No. 11/601,500 entitled "SOLID STATE BACKLIGHTING UNIT ASSEMBLY AND
METHODS" filed Nov. 17, 2006, the disclosure of which is incorporated
herein by reference.

[0047]The LED chips 16A-16D may include at least a red LED 16A, a green
LED 16B and a blue LED 16C. The blue and/or green LEDs may be InGaN-based
blue and/or green LED chips available from Cree, Inc., the assignee of
the present invention. The red LEDs may be, for example, AlInGaP LED
chips available from Epistar Corporation, Osram Opto Semiconductors GmbH,
and others. The lighting device 12 may include an additional green LED
16D in order to make more green light available.

[0048]In some embodiments, the LEDs 16A-16D may have a square or
rectangular periphery with an edge length of about 900 μm or greater
(i.e. so-called "power chips." However, in other embodiments, the LED
chips 16A-16D may have an edge length of 500 μm or less (i.e.
so-called "small chips"). In particular, small LED chips may operate with
better electrical conversion efficiency than power chips. For example,
green LED chips with a maximum edge dimension less than 500 microns and
as small as 260 microns, commonly have a higher electrical conversion
efficiency than 900 micron chips, and are known to typically produce 55
lumens of luminous flux per Watt of dissipated electrical power and as
much as 90 lumens of luminous flux per Watt of dissipated electrical
power.

[0049]As further illustrated in FIG. 2, the LEDs 16A-16D may be covered by
an encapsulant 14, which may be clear and/or may include light scattering
particles, phosphors, and/or other elements to achieve a desired emission
pattern, color and/or intensity. While not illustrated in FIG. 2, the
lighting device 12 may further include a reflector cup surrounding the
LEDs 16A-16D, a lens mounted above the LEDs 16A-16D, one or more heat
sinks for removing heat from the lighting device, an electrostatic
discharge protection chip, and/or other elements.

[0050]LED chips 16A-16D of the lighting elements 12 in the tile 10 may be
electrically interconnected as shown in the schematic circuit diagram in
FIG. 3. As shown therein, the LEDs may be interconnected such that the
blue LEDs 16A in the first path 20 are connected in series to form a
string 20A. Likewise, the first green LEDs 16B in the first path 20 may
be arranged in series to form a string 20B, while the second green LEDs
16D may be arranged in series to form a separate string 20D. The red LEDs
16C may be arranged in series to form a string 20C. Each string 20A-20D
may be connected to an anode contact 22A-22D arranged at a first end of
the tile 10 and a cathode contact 24A-24D arranged at the second end of
the tile 10, respectively.

[0051]A string 20A-20D may include all, or less than all, of the
corresponding LEDs in the first path 20 or the second path 21. For
example, the string 20A may include all of the blue LEDs from all of the
lighting elements 12 in the first path 20. Alternatively, a string 20A
may include only a subset of the corresponding LEDs in the first path 20.
Accordingly the first path 20 may include four serial strings 20A-20D
arranged in parallel on the tile 10.

[0052]The second path 21 on the tile 10 may include four serial strings
21A, 21B, 21C, 21D arranged in parallel. The strings 21A to 21D are
connected to anode contacts 26A to 26D, which are arranged at the second
end of the tile 10 and to cathode contacts 28A to 28D, which are arranged
at the first end of the tile 10, respectively.

[0053]It will be appreciated that, while the embodiments illustrated in
FIGS. 1-3 include four LED chips 16 per lighting device 12 which are
electrically connected to form at least four strings of LEDs 16 per path
20, 21, more and/or fewer than four LED chips 16 may be provided per
lighting device 12, and more and/or fewer than four LED strings may be
provided per path 20, 21 on the tile 10. For example, a lighting device
12 may include only one green LED chip 16B, in which case the LEDs may be
connected to form three strings per path 20, 21. Likewise, in some
embodiments, the two green LED chips in a lighting device 12 may be
connected in series to one another, in which case there may only be a
single string of green LED chips per path 20, 22. Further, a tile 10 may
include only a single path 20 instead of plural paths 20, 21 and/or more
than two paths 20, 21 may be provided on a single tile 10.

[0054]Multiple tiles 10 may be assembled to form a larger lighting bar
assembly 30 as illustrated in FIG. 4A. As shown therein, a bar assembly
30 may include two or more tiles 10, 10', 10'' connected end-to-end.
Accordingly, referring to FIGS. 3 and 4A, the cathode contacts 24 of the
first path 20 of the leftmost tile 10 may be electrically connected to
the anode contacts 22 of the first path 20 of the central tile 10', and
the cathode contacts 24 of the first path 20 of the central tile 10' may
be electrically connected to the anode contacts 22 of the first path 20
of the rightmost tile 10'', respectively. Similarly, the anode contacts
26 of the second path 21 of the leftmost tile 10 may be electrically
connected to the cathode contacts 28 of the second path 21 of the central
tile 10', and the anode contacts 26 of the second path 21 of the central
tile 10' may be electrically connected to the cathode contacts 28 of the
second path 21 of the rightmost tile 10'', respectively.

[0055]Furthermore, the cathode contacts 24 of the first path 20 of the
rightmost tile 10'' may be electrically connected to the anode contacts
26 of the second path 21 of the rightmost tile 10'' by a loopback
connector 35. For example, the loopback connector 35 may electrically
connect the cathode 24A of the string 20A of blue LED chips 16A of the
first path 20 of the rightmost tile 10'' with the anode 26A of the string
21A of blue LED chips of the second path 21 of the rightmost tile 10''.
In this manner, the string 20A of the first path 20 may be connected in
series with the string 21A of the second path 21 by a conductor 35A of
the loopback connector 35 to form a single string 23A of blue LED chips
16. The other strings of the paths 20, 21 of the tiles 10, 10', 10'' may
be connected in a similar manner.

[0056]The loopback connector 35 may include an edge connector, a flexible
wiring board, or any other suitable connector. In addition, the loop
connector may include printed traces formed on/in the tile 10.

[0057]While the bar assembly 30 shown in FIG. 4A is a one dimensional
array of tiles 10, other configurations are possible. For example, the
tiles 10 could be connected in a two-dimensional array in which the tiles
10 are all located in the same plane, or in a three dimensional
configuration in which the tiles 10 are not all arranged in the same
plane. Furthermore the tiles 10 need not be rectangular or square, but
could, for example, be hexagonal, triangular, or the like.

[0058]Referring to FIG. 4B, in some embodiments, a plurality of bar
assemblies 30 may be combined to form a lighting panel 40, which may be
used, for example, as a backlighting unit (BLU) for an LCD display. As
shown in FIG. 4B, a lighting panel 40 may include four bar assemblies 30,
each of which includes six tiles 10. The rightmost tile 10 of each bar
assembly 30 includes a loopback connector 35. Accordingly, each bar
assembly 30 may include four strings 23 of LEDs (i.e. one red, two green
and one blue).

[0059]In some embodiments, a bar assembly 30 may include four LED strings
23 (one red, two green and one blue). Thus, a lighting panel 40 including
nine bar assemblies may have 36 separate strings of LEDs. Moreover, in a
bar assembly 30 including six tiles 10 with eight solid state lighting
elements 12 each, an LED string 23 may include 48 LEDs connected in
serial.

[0060]For some types of LEDs, in particular blue and/or green LEDs, the
forward voltage (Vf) may vary by as much as +/-0.75V from a nominal value
from chip to chip at a standard drive current of 20 mA. A typical blue or
green LED may have a Vf of 3.2 Volts. Thus, the forward voltage of such
chips may vary by as much as 25%. For a string of LEDs containing 48
LEDs, the total Vf required to operate the string at 20 mA may vary by as
much as +/-36V.

[0061]Accordingly, depending on the particular characteristics of the LEDs
in a bar assembly, a string of one light bar assembly (e.g., the blue
string) may require significantly different operating power compared to a
corresponding string of another bar assembly. These variations may
significantly affect the color and/or brightness uniformity of a lighting
panel that includes multiple tiles 10 and/or bar assemblies 30, as such
Vf variations may lead to variations in brightness and/or hue from tile
to tile and/or from bar to bar. For example, current differences from
string to string may result in large differences in the flux, peak
wavelength, and/or dominant wavelength output by a string. Variations in
LED drive current on the order of 5% or more may result in unacceptable
variations in light output from string to string and/or from tile to
tile. Such variations may significantly affect the overall color gamut,
or range of displayable colors, of a lighting panel.

[0062]In addition, the light output characteristics of LED chips may
change during their operational lifetime. For example, the light output
by an LED may change over time and/or with ambient temperature.

[0063]In order to provide consistent, controllable light output
characteristics for a lighting panel, some embodiments of the invention
provide a lighting panel having two or more serial strings of LED chips.
An independent current control circuit is provided for each of the
strings of LED chips. Furthermore, current to each of the strings may be
individually controlled, for example, by means of pulse width modulation
(PWM) and/or pulse frequency modulation (PFM). The width of pulses
applied to a particular string in a PWM scheme (or the frequency of
pulses in a PFM scheme) may be based on a pre-stored pulse width
(frequency) value that may be modified during operation based, for
example, on a user input and/or a sensor input.

[0064]Accordingly, referring to FIG. 5, a lighting panel system 200 is
shown. The lighting panel system 200, which may be a backlight for an LCD
display panel, includes a lighting panel 40. The lighting panel 40 may
include, for example, a plurality of bar assemblies 30, which, as
described above, may include a plurality of tiles 10. However, it will be
appreciated that embodiments of the invention may be employed in
conjunction with lighting panels formed in other configurations. For
example, some embodiments of the invention may be employed with solid
state backlight panels that include a single, large area tile.

[0065]In particular embodiments, however, a lighting panel 40 may include
a plurality of bar assemblies 30, each of which may have four cathode
connectors and four anode connectors corresponding to the anodes and
cathodes of four independent strings 23 of LEDs each having the same
dominant wavelength. For example, each bar assembly 30 may have a red
string, two green strings, and a blue string, each with a corresponding
pair of anode/cathode contacts on one side of the bar assembly 30. In
particular embodiments, a lighting panel 40 may include nine bar
assemblies 30. Thus, a lighting panel 40 may include 36 separate LED
strings.

[0066]A current driver 220 provides independent current control for each
of the LED strings 23 of the lighting panel 40. For example, the current
driver 220 may provide independent current control for 36 separate LED
strings in the lighting panel 40. The current driver 220 may provide a
constant current source for each of the 36 separate LED strings of the
lighting panel 40 under the control of a controller 230. In some
embodiments, the controller 230 may be implemented using an 8-bit
microcontroller such as a PIC18F8722 from Microchip Technology Inc.,
which may be programmed to provide pulse width modulation (PWM) control
of 36 separate current supply blocks within the driver 220 for the 36 LED
strings 23.

[0067]Pulse width information for each of the 36 LED strings 23 may be
obtained by the controller 230 from a color management unit 260, which
may in some embodiments include a color management controller such as the
Agilent HDJD-J822-SCR00 color management controller.

[0068]The color management unit 260 may be connected to the controller 230
through an I2C (Inter-Integrated Circuit) communication link 235. The
color management unit 260 may be configured as a slave device on an I2C
communication link 235, while the controller 230 may be configured as a
master device on the link 235. I2C communication links provide a
low-speed signaling protocol for communication between integrated circuit
devices. The controller 230, the color management unit 260 and the
communication link 235 may together form a feedback control system
configured to control the light output from the lighting panel 40. The
registers R1-R9, etc., may correspond to internal registers in the
controller 230 and/or may correspond to memory locations in a memory
device (not shown) accessible by the controller 230.

[0069]The controller 230 may include a register, e.g. registers R1-R9,
G1A-G9A, B1-B9, G1B-G9B, for each LED string 23, i.e. for a lighting unit
with 36 LED strings 23, the color management unit 260 may include at
least 36 registers. Each of the registers is configured to store pulse
width information for one of the LED strings 23. The initial values in
the registers may be determined by an initialization/calibration process.
However, the register values may be adaptively changed over time based on
user input 250 and/or input from one or more sensors 240A-C coupled to
the lighting panel 40.

[0070]The sensors 240A-C may include, for example, a temperature sensor
240A, one or more photosensors 240B, and/or one or more other sensors
240C. In particular embodiments, a lighting panel 40 may include one
photosensor 240B for each bar assembly 30 in the lighting panel. However,
in other embodiments, one photosensor 240B could be provided for each LED
string 30 in the lighting panel. In other embOdiments, each tile 10 in
the lighting panel 40 may include one or more photosensors 240B.

[0071]In some embodiments, the photosensor 240B may include
photo-sensitive regions that are configured to be preferentially
responsive to light having different dominant wavelengths. Thus,
wavelengths of light generated by different LED strings 23, for example a
red LED string 23A and a blue LED string 23C, may generate separate
outputs from the photosensor 240B. In some embodiments, the photosensor
240B may be configured to independently sense light having dominant
wavelengths in the red, green and blue portions of the visible spectrum.
The photosensor 240B may include one or more photosensitive devices, such
as photodiodes. The photosensor 240B may include, for example, an Agilent
HDJD-S831-QT333 tricolor photo sensor.

[0072]Sensor outputs from the photosensors 240B may be provided to the
color management unit 260, which may be configured to sample such outputs
and to provide the sampled values to the controller 230 to adjust the
register values for corresponding LED strings 23 to correct variations in
light output on a string-by-string basis. In some embodiments, an
application specific integrated circuit (ASIC) may be provided on each
tile 10 along with one or more photosensors 240B in order to pre-process
sensor data before it is provided to the color management unit 260.
Furthermore, in some embodiments, the sensor output and/or ASIC output
may be sampled directly by the controller 230.

[0073]The photosensors 240B may be arranged at various locations within
the lighting panel 40 in order to obtain representative sample data.
Alternatively and/or additionally, light guides such as optical fibers
may be provided in the lighting panel 40 to collect light from desired
locations. In that case, the photosensors 240B need not be arranged
within an optical display region of the lighting panel 40, but could be
provided, for example, on the back side of the lighting panel 40.
Further, an optical switch may be provided to switch light from different
light guides which collect light from different areas of the lighting
panel 40 to a photosensor 240B. Thus, a single photosensor 240B may be
used to sequentially collect light from various locations on the lighting
panel 40.

[0074]The user input 250 may be configured to permit a user to selectively
adjust attributes of the lighting panel 40, such as color temperature,
brightness, hue, etc., by means of user controls such as input controls
on an LCD panel.

[0075]The temperature sensor 240A may provide temperature information to
the color management unit 260 and/or the controller 230, which may adjust
the light output from the lighting panel on a string-to-string and/or
color-to-color basis based on known/predicted brightness vs. temperature
operating characteristics of the LED chips 16 in the strings 23.

[0076]Various configurations of photosensors 240B are shown in FIGS.
6A-6D. For example, in the embodiments of FIG. 6A, a single photosensor
240B is provided in the lighting panel 40. The photosensor 240B may be
provided at a location where it may receive an average amount of light
from more than one tile/string in the lighting panel.

[0077]In order to provide more extensive data regarding light output
characteristics of the lighting panel 40, more than one photosensor 240B
may be used. For example, as shown in FIG. 6B, there may be one
photosensor 240B per bar assembly 30. In that case, the photosensors 240B
may be located at ends of the bar assemblies 30 and may be arranged to
receive an average/combined amount of light emitted from the bar assembly
30 with which they are associated.

[0078]As shown in FIG. 6C, photosensors 240B may be arranged at one or
more locations within a periphery of the light emitting region of the
lighting panel 40. However in some embodiments, the photosensors 240B may
be located away from the light emitting region of the lighting panel 40,
and light from various locations within the light emitting region of the
lighting panel 40 may be transmitted to the sensors 240B through one or
more light guides. For example, as shown in FIG. 6D, light from one or
more locations 249 within the light emitting region of the lighting panel
40 is transmitted away from the light emitting region via light guides
247, which may be optical fibers that may extend through and/or across
the tiles 10. In the embodiments illustrated in FIG. 6D, the light guides
247 terminate at an optical switch 245, which selects a particular guide
247 to connect to the photosensor 240B based on control signals from the
controller 230 and/or from the color management unit 260. It will be
appreciated, however, that the optical switch 245 is optional, and that
each of the light guides 245 may terminate at a photosensor 240B. In
further embodiments, instead of an optical switch 245, the light guides
247 may terminate at a light combiner, which combines the light received
over the light guides 247 and provides the combined light to a
photosensor 240B. The light guides 247 may extend across partially across
and/or through the tiles 10. For example, in some embodiments, the light
guides 247 may run behind the panel 40 to various light collection
locations and then run through the panel at such locations. Furthermore,
the photosensor 240B may be mounted on a front side of the panel (i.e. on
the side of the panel 40 on which the lighting devices 16 are mounted) or
on a reverse side of the panel 40 and/or a tile 10 and/or bar assembly
30.

[0079]Referring now to FIG. 7, a current driver 220 may include a
plurality of bar driver circuits 320A-320D. One bar driver circuit
320A-320D may be provided for each bar assembly 30 in a lighting panel
40. In the embodiments shown in FIG. 7, the lighting panel 40 includes
four bar assemblies 30. However, in some embodiments the lighting panel
40 may include nine bar assemblies 30, in which case the current driver
220 may include nine bar driver circuits 320. As shown in FIG. 8, in some
embodiments, each bar driver circuit 320 may include four current supply
circuits 340A-340D, i.e., one current supply circuit 340A-340D for each
LED string 23A-23D of the corresponding bar assembly 30. Operation of the
current supply circuits 340A-340B may be controlled by control signals
342 from the controller 230.

[0080]The current supply circuits 340A-340B are configured to supply
current to the corresponding LED strings 13 while a pulse width
modulation signal PWM for the respective strings 13 is a logic HIGH.
Accordingly, for each timing loop, the PWM input of each current supply
circuit 340 in the driver 220 is set to logic HIGH at the first clock
cycle of the timing loop. The PWM input of a particular current supply
circuit 340 is set to logic LOW, thereby turning off current to the
corresponding LED string 23, when a counter in the controller 230 reaches
the value stored in a register of the controller 230 corresponding to the
LED string 23. Thus, while each LED string 23 in the lighting panel 40
may be turned on simultaneously, the strings may be turned off at
different times during a given timing loop, which would give the LED
strings different pulse widths within the timing loop. The apparent
brightness of an LED string 23 may be approximately proportional to the
duty cycle of the LED string 23, i.e., the fraction of the timing loop in
which the LED string 23 is being supplied with current.

[0081]An LED string 23 may be supplied with a substantially constant
current during the period in which it is turned on. By manipulating the
pulse width of the current signal, the average current passing through
the LED string 23 may be altered even while maintaining the on-state
current at a substantially constant value. Thus, the dominant wavelength
of the LEDs 16 in the LED string 23, which may vary with applied current,
may remain substantially stable even though the average current passing
through the LEDs 16 is being altered. Similarly, the luminous flux per
unit power dissipated by the LED string 23 may remain more constant at
various average current levels than, for example, if the average current
of the LED string 23 were being manipulated using a variable current
source.

[0082]The value stored in a register of the controller 230 corresponding
to a particular LED string may be based on a value received from the
color management unit 260 over the communication link 235. Alternatively
and/or additionally, the register value may be based on a value and/or
voltage level directly sampled by the controller 230 from a sensor 240.

[0083]In some embodiments, the color management unit 260 may provide a
value corresponding to a duty cycle (i.e. a value from 0 to 100), which
may be translated by the controller 230 into a register value based on
the number of cycles in a timing loop. For example, the color management
unit 260 indicates to the controller 230 via the communication link 235
that a particular LED string 23 should have a duty cycle of 50%. If a
timing loop includes 10,000 clock cycles, then assuming the controller
increments the counter with each clock cycle, the controller 230 may
store a value of 5000 in the register corresponding to the LED string in
question. Thus, in a particular timing loop, the counter is reset to zero
at the beginning of the loop and the LED string 23 is turned on by
sending an appropriate PWM signal to the current supply circuit 340
serving the LED string 23. When the counter has counted to a value of
5000, the PWM signal for the current supply circuit 340 is reset, thereby
turning the LED string off.

[0084]In some embodiments, the pulse repetition frequency (i.e. pulse
repetition rate) of the PWM signal may be in excess of 60 Hz. In
particular embodiments, the PWM period may be 5 ms or less, for an
overall PWM pulse repetition frequency of 200 Hz or greater. A delay may
be included in the loop, such that the counter may be incremented only
100 times in a single timing loop. Thus, the register value for a given
LED string 23 may correspond directly to the duty cycle for the LED
string 23. However, any suitable counting process may be used provided
that the brightness of the LED string 23 is appropriately controlled.

[0085]The register values of the controller 230 may be updated from time
to time to take into account changing sensor values. In some embodiments,
updated register values may be obtained from the color management unit
260 multiple times per second.

[0086]Furthermore, the data read from the color management unit 260 by the
controller 230 may be filtered to limit the amount of change that occurs
in a given cycle. For example, when a changed value is read from the
color management unit 260, an error value may be calculated and scaled to
provide proportional control ("P"), as in a conventional PID
(Proportional-Integral-Derivative) feedback controller. Further, the
error signal may be scaled in an integral and/or derivative manner as in
a PID feedback loop. Filtering and/or scaling of the changed values may
be performed in the color management unit 260 and/or in the controller
230.

[0087]In some embodiments, calibration of a display system 200 may be
performed by the display system itself (i.e. self-calibration), for
example, using signals from photosensors 240B. However, in some
embodiments of the invention, calibration of a display system 200 may be
performed by an external calibration system.

[0088]The user input 250 may specify a color point that is to be displayed
by the lighting panel 40. In order to improve the overall performance of
the system, it may be desirable to restrict the gamut of colors that may
be displayed by the lighting panel 40. This may be particularly important
for closed loop control mode in which large numbers of calculations maybe
performed in a calibration process.

[0089]For example, FIG. 9A is an approximate representation of a 1931 CIE
chromaticity diagram. The 1931 CIE chromaticity diagram is a
two-dimensional color space in which all visible colors are uniquely
represented by a set of (x,y) coordinates. Other two-dimensional color
spaces are known in the art.

[0090]Referring to FIG. 9A, fully saturated (i.e. pure) colors fall on the
outside edge of the 1931 CIE chromaticity diagram, as indicated by the
wavelength numbers running from 380 nm to 700 nm on the chart. Fully
unsaturated light, which is white, is found near the center of the chart.
A blackbody radiation curve 420 (shown as a partial approximation in FIG.
9A) plots the color point of light emitted by a blackbody radiator at
various temperatures. The blackbody radiation curve 420 runs through the
"white" region of the CIE diagram. Accordingly, some "white" points may
be associated with particular color temperatures.

[0091]An exemplary actual gamut of a lighting panel system 200, that is,
the range of colors that could potentially be displayed by the lighting
panel system 200, is shown in FIG. 9A as the triangle 405. The actual
gamut is determined by the wavelength and saturation of the LED light
sources used in the backlight 40. The CIE chromaticity diagram shown in
FIG. 9A also shows a possible limited gamut or region 400A for a lighting
panel system 200 according to some embodiments of the invention.

[0092]The region 400A may be defined as a region in which the
x-coordinates and the y-coordinates fall within a defined range. In some
embodiments, the defined range may include a rectangle. For example, the
x coordinate may be restricted such that x is greater than or equal to a
first limit (x≧xlim1) and x is less than or equal to a second
limit (x≦xlim2). Similarly, the y coordinate may be restricted
such that y is greater than or equal to a first limit (y≧ylim1)
and y is less than or equal to a second limit (y≦ylim2).

[0093]In particular, the region 400A illustrated in FIG. 9A is bounded by
the rectangle 410A defined by the following equations:

0.26≦x≦0.38 (1)

0.26≦y≦0.38 (2)

[0094]If the user requests, for example via the user input 250, a color
point outside the region 400A (such as point A), the coordinates of the
point selected by the user may be automatically truncated to the closest
point within/on the rectangle 410A (e.g. point B). In this case, the
x-coordinate of the requested point A would be reduced to 0.38, so that
the actual color point (point B) would be at the edge of the rectangle
410A.

[0095]In the example illustrated in FIG. 9A, only the x-coordinate of
point A is outside the acceptable range defined by Equations (1) and (2).
Thus, the modified color point B may be obtained by limiting only the
x-coordinate of the requested color point A. In comparison, both the x-
and y-coordinates of a requested color point A' are outside the
acceptable range defined by the region 400A. Thus, both the x- and
y-coordinates of the requested color point A' may be modified such that
the modified color point B' may lie at a corner of the rectangle 410A.

[0096]The region 400A encompassed by the rectangle 410A may include a
desirable region of the blackbody curve for a white point for an LCD
backlight. However, other regions besides those defined by the rectangle
410A could be chosen.

[0097]Furthermore, the restricted region may be defined other ways besides
a box. For example, as shown in FIG. 9B, a restricted region 400B may be
defined by a circle 410B as all color points within a predetermined
distance (r) from a reference color point C. If the user requests a color
point outside the region 400B (such as point A), the coordinates of the
point selected by the user may be translated to the closest point
within/on the circle 410B (e.g. point B). In some cases, the requested
color point may be moved along a line directed from the specified color
point A to the central color point C, until the target color point just
reaches the edge of the region 400B at point B, so that the modified
color point (point B) would be at the edge of the circle 410B.

[0098]Referring to FIG. 9c, a restricted region 400C may be defined by a
regular or irregular polygon 410C. If the user requests a color point
outside the region 400C (such as point A), the coordinates of the point
selected by the user may be translated to the closest point within/on the
polygon 410C (e.g. point B). In some cases, the requested color point may
be moved from the specified color point A toward the closest point on the
polygon 410C, until the target color point just reaches the edge of the
region 400C at point B, so that the actual color point (point B) would be
at the edge of the polygon 410C. In some embodiments, the color point may
be moved toward a reference color point (e.g. point C) until the color
point is within/on the polygon 410C, e.g. at point B'.

[0099]Referring to FIG. 9D, a restricted region 400D may be defined as all
color points within a predetermined distance from the blackbody radiation
curve 420. If the user requests a color point outside the region 400D
(such as point A) that defines all points within a predetermined distance
from the blackbody radiation curve 420, the coordinates of the point
selected by the user may be moved toward the closest point on the
blackbody radiation curve 420 until the color point is within the
predetermined distance from the blackbody radiation curve 420 (e.g. point
B). In some embodiments, the color point may be moved toward a reference
color point (e.g. point C) until the color point is within a
predetermined distance from the blackbody radiation curve 420, e.g. at
point B'.

[0100]Other criteria may be used to define the extent of a restricted
region, including any combination of the above described criteria. For
example, a restricted region may be defined as all color points within a
predetermined distance from the blackbody radiation curve 420 and within
a predefined distance of a defined color point, all color points within a
predetermined distance from the blackbody radiation curve 420 and having
an x-coordinate within a predetermined interval on the 1931 CIE
chromaticity diagram (e.g. 0.260<x<0.380), etc.

[0101]A flowchart of operations is shown in FIG. 10. As illustrated
therein, a color point request is received by the controller 230, for
example, via the user input 250 (Block 1310). Color point requests may be
received by the controller 230 from other sources, such as from a
computer system unit to which the display 200 is attached. The controller
230 analyzes the requested color point and determines if the color point
is within acceptable limits (Block 1320). For example, the controller 230
may determine if the requested color point falls within a restricted
region 400, such as a box or other polygon, within a predetermined
distance from a specified color point, within a predetermined distance
from the blackbody radiation curve, etc.

[0102]If the requested color point is not within an acceptable limit, the
controller 230 calculates a modified color point based on the requested
color point (Block 1330). The original or modified color point is then
applied by the controller 230 to the lighting panel 40 (Block 1340).

[0103]In some embodiments, the system may permit the user to select only
from among predetermined color setpoints (e.g., the D65 setpoint, the D55
setpoint, etc.) and/or from predetermined color temperatures.
Predetermined setpoints have been included in conventional LCD displays
monitors. However, in a conventional LCD display, that functionality is
not implemented by changing the color point of the backlight, but rather
is implemented by changing the duty cycles of the LCD shutters. For
example, in a conventional LCD, the color setpoint may be adjusted by
altering the relative duty cycle of the LCD shutters of one color versus
the duty cycle of the shutters of another color to effect an apparent
change in the color point of the display. However, the conventional
approach may reduce the efficiency and/or the brightness of the display,
since one of the colors may be dimmed relative to another color. Some
embodiments of the present invention may permit a user to directly change
the color setpoint of the backlight without having to alter the operation
of the LCD shutters, which may reduce the complexity of the display
and/or may increase the efficiency of the display.

[0104]In the drawings and specification, there have been disclosed typical
embodiments of the invention and, although specific terms are employed,
they are used in a generic and descriptive sense only and not for
purposes of limitation, the scope of the invention being set forth in the
following claims.